The invention described herein was made in the course of, or under, a contract with the U.S. ATOMIC ENERGY COMMISSION. It relates to apparatus and method for minimizing self focusing caused by diffraction in high-power laser amplifier systems.
High-power laser amplifier systems, e.g., Nd:glass, are plagued by damage to components which often results from selffocusing. Self-focusing in such systems can be prematurely induced by severe spatial modulation of the beam intensity profile. These oscillations result from diffraction caused by sharp truncation of the beam at the input edges of rods, disks, and other components. Severe truncation is difficult to avoid since it is desirable for the incident beam to fill the amplifier apertures to obtain maxiumum extraction of energy. An intensity profile which minimizes damage caused by diffraction-produced hot spots and still utilizes nearly all of the useful aperture of laser amplifiers has been disclosed by Campillo et al. in "Fresnel Diffraction Effects in the Design of High-power Laser Systems," 23 Appl. Phys. Lett. 85 (1973). Diffraction smoothing apertures are known in the art.